Heat pump systems



y 3, 1962 J. R. HARNISH 3,041,849

HEAT PUMP SYSTEMS Filed Sept. 25, 1959 IN VEN TOR. Janis RJ/Amv/s/I.

United States Patent Ofifice 3,041,849 Patented July 3, 1962 3,041,849 HEAT PUMP SYSTEMS James R. Hamish, York, lPa., assignor to Borg-Warner Corporation, Chicago, llL, a corporation of Illinois Filed Sept. 25, 1959, Ser. No. 842,504 6 Claims. (Cl. 62--215) This invention relates to air source heat pump systems, and, more specifically, to a single stage heat pump system.

In an air source heat pump system, as the temperature of the air drops, the capacity of the system likewise drops at the very time when heating requirements are the greatest. Various methods have been devised to ofifset this decrease in capacity. These take the form of electric supplementary heat, compound compression systems, etc.

Generally, on single stage air source heat pump systems, the compressor is selected for the cooling operation, resulting in an oversized compressor for the heating operation. The horsepower required by the compressor is a function of both the suction pressure and the discharge pressure. For the cooling operation, the suction pressure is relatively constant at between approximately 35 F. and 40 F. equivalent temperature. During the heating operation, the evaporator temperature, on colder days, is well below this, resulting in a considerably lower equivalent suction pressure. This results in a lower density refrigerant gas being handled by the compressor and, since the discharge pressure in heating does not vary very much from that in cooling, there is a consequent reduction in horsepower required. Thus, if a compressor is selected for cooling operation, it requires a given motor size, and when used on heating operation, extra motor capacity is available over and above that required for full load operation.

Applicant has devised a relatively simple and inexpensive method of providing additional capacity. In selecting the compressor capacity, additional compression cylinders are provided over and above that required for the cooling load. For example, the system may require six cylinders to provide design cooling requirements. However, an eight cylinder compressor would be provided having a motor only sufliciently large to handle the six cylinder cooling load. During the cooling operation, the two extra cylinders will be maintained auto matically unloaded.

For operation on colder days, the two additional cylinders would automatically come into operation. Since the compressor horsepower per cylinder is substantially less at the lower evaporator temperatures involved on cold days, the motor selected for cooling (six cylinders) is sufliciently large to handle eight cylinders for this condition.

This arrangement is particularly attractive on most single stage systems when electric supplementary heat must be provided at lower outdoor air temperatures. It requires the additional expense only for a larger compressor to provide the additional heat required, and the electric heaters can be eliminated or held to a minimum. The motor and starter size, wiring and other equipment, need not be increased in size.

It is an object of the invention, therefore, to provide in a heat pump system a multi-cylinder compressor having means for unloading at least one of the cylinders during cooling operation and for operating the compressor fully loaded during low temperature heating operation, and having a motor sized for the unloaded cooling operation.

Another object of the invention is to provide a heat pump system, including a motor-compressor unit, wherein the motor is used to its fullest capacity during both cooling and heating operation, the compressor comprising multi-cylinder compression means sized for partially unloaded operation during the cooling operation and for fully loaded operation during low-temperature heating operation. Yet another object of the invention is to provide a heat pump system of the type above-mentioned, wherein means are provided for automatically unloading at least one compressor cylinder above a certain preselected outside air temperature.

The invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above-stated objects and such other objects as will appear from the following description of preferred embodiments of the invention described with reference to the accompanying drawings, in which:

FIG. 1 comprises a diagrammatic representation of a heat pump system embodying the invention; and

FIG. 2 is a partial view shomng a four-way reversing valve in its alternate position.

Like numerals refer to like parts throughout the two views.

Turning now to FIG. 1, a compressor 10 is driven by an electric motor 11 by way of a belt drive 12. An indoor heat-exchanger 13 and an outdoor heat-exchanger 14 are provided and are connected together by way of a liquid line 15, including a capillary 16 therein.

A typical four-way valve 17 serves to direct refrigerant from compressor 10 to the outdoor heat-exchanger 14 or the indoor heat-exchanger 13, depending on whether cooling or heating is desired. The discharge of compressor 10 is connected with four-way valve 17 by way of a gas line 18. A gas line 19 leads from the four-way valve 17 back to the suction of compressor 10. A gas line 20 leads from indoor heat-exchanger 13 to four-way valve 17, and a gas line 21 similarly extends between outdoor heat-exchanger 14 to four-way valve 17.

In denoting heat-exchangers 13 and 14 as indoor and outdoor, I am referring to their function rather than their physical location.

Indoor heat-exchanger 13 is in heat-exchange relation with air to be conditioned and supplied a building, while outdoor heat-exchanger 14 is in heat-exchange relation with outside air, dissipating heat thereto or picking up heat therefrom.

A compressor cylinder unloading mechanism 22 is provided for unloading one or more cylinders of compressor 10, and is controlled by bulb 23 located in the outdoor air stream and connected to unloading mechanism 22 by way of a capillary 24. Bulb 23 contains a volatile fluid so chosen as to develop suflicient pressure at the desired temperature to actuate unloader mechanism 22.

The compressor unloading mechanism is not shown in greater detail since it may take any preferred form and is no part of the invention per so. For example, the compressor and its loading and unloading mechanism may be that type shown in the Aldinger Patent No. 2,526,922, owned by the assignee of my invention. For the purpose of this disclosure, the Aldinger disclosure is by reference incorporated herein.

As was pointed out hereinabove, compressor 10 comprises a multi-cylinder compression means driven by motor 11, selected such that it is only sufliciently large to handle the fully loaded, low temperature heating load.

In operation and during the cooling operation, the volatile fluid within bulb 23 transmits sufiicient pressure through capillary 24 to unloader mechanism 22 to unload one or more cylinders of compressor 10, all as may be understood from an inspection of the aforementioned Aldinger Patent No. 2,526,922. Pour-way valve 17 is set as shown and refrigerant gas compressed in compressor 10 flows into line 18 and is directed by four-Way valve 17 into line 21, whence it flows into the outdoor heatexchanger 14. The gas which is liquified in flow therethrough, flows into line 15 and through capillary 16 enroute to indoor heat-exchanger 13. Passing through capillary 16, its pressure and corresponding temperature are dropped to a point Where heat may be picked up from the air flowing over indoor heat-exchanger 13. The refrigerant is evaporated and the gas thence flows by way of line 20 to four-way valve 17 and is directed into line 19 back to the inlet of the compressor to complete the cycle. As was mentioned, electric motor 11 is of a size only sufficiently large to operate compressor 10 in its unloaded condition during the cooling operation.

As the outside temperature drops, the system goes on heating operation and four-way valve 17 is reversed, thereby reversing the function of indoor heat-exchanger 13 and outdoor heat-exchanger 14. The indoor heatexchanger 13 now operates as a refrigerant condenser and the outdoor heat-exchanger 14 operates as a refrigerant evaporator. As the outdoor temperature continues to drop and at some preselected temperature, pressure developed within bulb 23 is insufficient to actuate unloader 22 to maintain compressor 1% in its unloaded condition, and all the compressor cylinders may come into operation if required by the building heating load. However, because of the lower horsepower requirements per cylinder during low temperature operation, motor 11 is sufliciently large to maintain the compressor in operation. It will be apparent that more heat will be provided by the compressor with the additional cylinders in operation and at a cost only slightly more than would be the case if compressor 10 were sized for the cooling load. Further, motor 11 is used at optimum capacity at all times.

I wish it to be understood that my invention is not to be limited to the specific constructions and arrangements shown and described, except only insofar as the claims may be so limited, as it will be apparent to those skilled in the art that changes may be made without departing from the principles of the invention.

What is claimed is:

l. A heat pump comprising an outdoor heat-exchanger, and indoor heat-exchanger, and a compressor, said compressor comprising multi-cylinder compression means, refrigerant (flow lines connecting said compressor unit and heat-exchangers in a closed refrigerant circuit, means for directing refrigerant from said compressor through said closed refrigerant circuit, first to said outdoor heatexchanger during a cooling operation and first to said indoor heat-exchanger during a heating operation, means for expanding refrigerant in the second heat-exchanger of the series, means for maintaining at least one of said cylinders unloaded during said cooling operation and for operating said compressor fully loaded at least part time during said heating operation, and a motor only of sufiicient size to operate said compressor when unloaded during said unloaded cooling operation.

2. A heat pump as set out in claim 1, and automatic means for loading and unloading said cylinders according to a preselected outside air temperature.

3. A heat pump comprising an outdoor heat-exchanger, an indoor heat-exchanger, and a compressor, said compressor comprising multi-cylinder compression means, refrigerant flow lines connecting said compressor unit and heat-exchangers in a closed refrigerant circuit, means for directing refrigerant from said compressor through said closed refrigerant circuit first to said outdoor heatexchanger during a cooling operation and first to said in door heat-exchanger during a heating operation, means for expanding refrigerant in the second heat-exchanger of the series, means for maintaining at least one of said cylinders unloaded during said cooling operation and for fully loading said cylinders during said heating operation, and a motor only of sufficient size to operate said compressor when unloaded during said unloaded cooling operation.

4. In a heat pump comprising an outdoor heat-exchanger, an indoor heat-exchanger, a compressor, refrigerant fiow lines connecting said compressor unit and heatexchangers in a closed refrigerant circuit, means for directing refrigerant from said compressor through said closed refrigerant circuit first to said out-door heat-exchanger during a cooling operation and first to said indoor heat-exchanger during a heating operation and means for expanding refrigerant in the second heat-exchanger of the series, the improvement comprising a multi-cylinder compressor, means for maintaining at least one of said cylinders unloaded during said cooling operation and for operating said compressor fully loaded during low temperature heating operation, and a motor only of suflicient size to operate said compressor when unloaded during said unloaded cooling operation.

5. In a heat pump according to claim 4, means for automatically loading and unloading said compressor cylinders according to a predetermined low outside air temperature.

6. In a heat pump comprising an outdoor heat-exchanger, an indoor heat-exchanger, a compressor, refrigerant flow lines connecting said compressor unit and heat-exchangers in a closed refrigerant circuit, means for directing refrigerant from said compressor through said closed refrigerant circuit first to said outdoor heat-exchanger during a cooling operation and first to said indoor heat-exchanger during a heating operation and means for expanding refrigerant in the second heat-exchanger of the series; the improvement comprising a multi-cylinder compressor, means for maintaining at least one of said cylinders unloaded during said cooling operation and for fully loading said cylinders during said heating operation, and a motor only of suificient size to operate said compressor when unloaded during said unloaded cooling operation.

References Cited in the file of this patent UNITED STATES PATENTS 2,498,861 Newton Feb. 8, 1950 2,619,326 McLenegen Nov. 25, 1952 2,912,833 McGrath Nov. 17, 1959 

